The invention relates to optical interleaver devices, and in particular to birefringent crystal interleaver/deinterleavers for use in optical systems using wavelength division multiplexing or dense wavelength division multiplexing.
As telecommunications usage increases, as a result of increased internet usage, increased types of communications and population growth, telecommunications providers are required to provide greater voice- and data-carrying capacity. In order to reduce the cost and the amount of time required to provide the increased capacity, wavelength division multiplexing (WDM) and dense wavelength division multiplexing (DWDM) have been developed, which provide increased capacity without requiring new fiber optic cables.
WDM and DWDM technologies combine multiple optical signals into a single fiber by transporting different signals on different optical wavelengths or channels. Interleaving and deinterleaving of optical channels is typically accomplished with thin film optical filters. However, multiple layers of film are required to interleave and deinterleave multiple channels, which increases the cost and complexity of a component. Another disadvantage of multi-layer thin film filtering is that the thin films break down over time, especially when operating under high power conditions.
What is needed is an improved optical device for use with WDM and/or DWDM optical signals. Prior attempts to improve optical devices are disclosed in U.S. Pat. No. 4,566,761 issued Jan. 28, 1986 to Carlsen et al; U.S. Pat. No. 4,685,773 issued Aug. 11, 1987 to Carlsen et al; and U.S. Pat. No. 5,694,233 issued Dec. 2, 1997 to Wu et al, which are incorporated herein by reference.
The present invention relates to an interleaver/deinterleaver apparatus comprising:
a first port for inputting or outputting a first optical signal, which comprises a second optical signal comprising at least one wavelength channel from a first subset of channels and a third optical signal comprising at least one wavelength channel from a second subset of wavelength channels;
a second port for outputting or inputting the second optical signal;
a third port for outputting or inputting the third optical signal;
a birefringent assembly optically coupled to the first, second and third ports, whereby after a first pass through the birefringent assembly the second signal exits the birefringent assembly with a polarization orthogonal to the polarization of the third signal;
first beam splitting/combining means for separating the first signal input from the first port into the second signal and the third signal, or for combining the second signal input from the second port with the third signal input from the third port into the first signal; and
first reflecting means for directing the second and third signals separately back through the birefringent assembly for a second pass along second and third paths, respectively, for output via the second and third ports, respectively, or for reflecting the second and third signals, which traveled the second and third paths during a first pass, back together through the birefringent assembly for a second pass along the first path to the first port.